Discharge tube



Patented Sept. 28, 1943 l Y 2,830,600 Y BISCHARGETUBE.

Kuiperaindhoven, Netherlands; vested K l Qin the" Alien Property Custodian Application May 29, 1941, `Serial` No. 3955888 Y 4Irrthe Netherlands June 25, 1940 screams. (o1. 25o-27.5)

The present invention relates fito discharge tubesA and -tol a method dflmanufacturing .the same. More particularly-g-theinvention relates to vapour-lled discharge-tubes, for-examplemercury vapour Vdischarge tubesl` with incandescent cathodes; xr/hichfilling` is replenishedefrom a-supply of Vapour producing substance Lprovided inthe foot of the-tube. e v

It is-fknown to provide iin suohdisoharge tubes avapour-producing supplyin the doot off the v tube, preferably in asupplyf-vesselisp'ecially-provided for this purpose for inmostfcasesiitfis ypossible to construct the tube in such manner vt`ha.t-ltlf1e lower' partof the foot constitutes #the coldest point of= thedischarge vessel and 'the .required y low pressure can bethusmaintained;

It sometimes entails greatfdrawbacks when the vapour-producing materiallior'example the liquidfmercury, is--free to-move-withintheftube and -comesl into vcontact' the electrodes. Especially in incandescent cathode current-converting tubes Lfor Ehigh voltages therearises inithis haustedand filled, itis necessaryfto provide-fthe mercury temporarily inthe-v discharge vessel 'before `it is 'possible vto jsealmthe tube: -Morefparticularly after transportl of the-tube'it mayioccur that the vlatter'has tobe",burned"out" anewfat a reduced voltage before the tube can be-loaded at the 'full `allowable voltage; There areeven cases wherein it is no longer' possible to restore-themstance in the supply vessel, especially 'if 'theyre-l quirement. is made that jthis ymaterial should-be kept frenfioterfromr the .discharge space proper. n

. Theiinventonshas for its purpose toconstruct and to arrange the.l supply Lvesselin such,l manner that-the vapour-producingsupply mayrbe gintroduced in a very simple manner without freaching the .discharge space` andi that linvthisrmzzase neither during rtransport nor duringloperation of theftube does an `.excess otrvapour-producingsub,-y .e

stance penetrate into the discharge space. p

According to the 1 invention, 'theasllpply vessel for the( vapour-producing substancelarranged `in theA foot of the tube mayfbeyprovidedat; thefside of' and `preferably concentricall-p around ythe exhaust tube and communicatesfwithxthejlatteryin such manner `that during exhaustion ythe vapourproducingsubstance may be :introduced sinto.A the supply vesselfrom that end of. the exhausttube which is `remote V'froxn the discharge tubegwthout the substancebeing able to penetrate into that end of the tube which leads to 'thedischarge Space whilst the .latter end andtheA supplyrspace are connectedto :the otherend ofthe exhaust tubevthrough l,paths of low resistance 'to the 1cir l culation of gaseslor vapours.

This -orrn ofconstruction ,has vthe Laduantage that'the fsupplyvessel' comes `to alie,v as itlwere,.in

itiarbicekmg capacityorthe tube-wherimniy once mercury 'has deposited; Afor exampleon the suriace'oftheanode; i f

It is j already lknown'toprovidethe mercury -in such a casein a supply'vessel'iwiiiclrfcommuni- 'Cates `with"'the discharge'space'proper-*by-means of Va Inarrowed portion; for example a capillary tube.' Apart'from-theiact thatths'construction maygiverise'to mechanical inconveniencesfespeciallyas regardsltherisk ofcrach'ing of the capil-v laryM tube; there arises in this case thenecessity of= taking'parti'cula'r Lmeasures#during{manufaca side-branch ofthe exhaust tubefzsofithatf the vapour-producing, substanceA can vreach the gsup.n ply vessel from asupply'connectedl to the-.nexhaust'ing installation withoutfpenetratingdntofthe discharge space, Whilst it islvery simple to prever-rt vapour-producingmaterial from .fdstillin-gliover y tothe discharge `space by.Tmaiutai-nin'grr the` tem- Lperature of thesuppl-'y vessel and' the lower sex-r 'hausttube' below that .of the dscharge'-vessel 'andi the upper r exhaust ltub e:

itis." advantageous to out through.- the exhaust `'tube provided in' y:the-footof thef -dlsch'arge'tube fior; the reception of ,the supply' .vessel .and z to "ca'use `the tube portionswhich com'efzinto icommunication lwith --the vdischarge space; an'dlwith "the Aexhausting device respectively;@to-protrude 'in-alignment with` oneanotherat the upperf end andat `the lower end finto ithe-su-pply f/Vesseliand to extend up ito vthe immediate vicinityof -ion'e j anotherV so that the-interior spaceaof the exhaust -tube, which neither alters-sits Ydirection n'oriis I'narrowed lin any? way at this pointzoiilyiicom- '--municates' |with the supply spacethrough :an

annular #slitll havingefa fheirght of r3 c rimsiv `aft-:the

This construction may further be improved by closing those ends of the two portions of the exhaust tube which are turned towards one another by means of fine metallic gauze having a mesh width of 0.2 mm. at the most, for exam: ple of nickel wire and preferably in the shape of caps. If with this construction a drop of the vapour-producing material might reach the space between the pieces of gauze the latter still prevent in an efficient manner the material from penetrating into both portions of the exhaust tube. These caps of gauze do not give rise to an inadmissible circulation resistance for the gases or vapours pumped away or for the vapours passing from the vapour-producing supply to the discharge space.

The -invention will be explained more fully with reference to the accompanying drawing which represents, by way of example, two embodiments thereof.

Fig. 1 represents an incandescent cathode rectifying tube provided with a supply vessel according to the invention.

Fig. 2 shows one favourable form of construction of the supply vessel.

Fig. 1 represents a rectifying tube comprising a cylindrical glass vessel I, a directly heated incandescent cathode 2, and an anode 3. At one of the ends of the vessel I supply conductors 4 of the cathode are sealed into a pinch 5 and 4at the other end a supply conductor 6 of the anode is sealed into the glass wall by means of a chrome-iron plate 'L The cathode helix 2, which is directly heated and is provided with an activating layer of oxide, is surrounded by a cylindrical screen 8 which is conductively connected to one of the cathode poles and is constructed so as to be closed at the back-side of the cathode and open at the end turned towards the anode. On the circumference of the screen 8 there is a flat screening ring 9 which serves to prevent the passage of a discharge between the anode 3 and those parts of the space behind the cathode which have cathode potential. According to directions the maximum temperature of the supply of liquid mercury within the tube amounts to 50 C., which corresponds to a mercury vapour pressure of 12,5.10-3 mmsAof mercury. The anode 3 yis constituted by a cylinder open at one end. Said cylinder has been drawn from a sheet of nickel and blackened by carbonisation or in any other manner and surrounds the open end of the cathode screen in the way of a cup. Within the stem tube iI there is a glass tube I2 which acts during manufacture as the exhaust tube and in which is incorporated the supply vessel I3 for liquid mercury I4. According to the requirements set by the ambient temperature or by the manner of arrangement of the tube, the temperature of this supply, which determines the vapour pressure of the tube, may be regulated during manufacture once forall by arranging the vessel in the exhaust tube `at a higher or lower level. During exhaustion the mercury may be introduced from below through the exhaust tube and over the lengthening piece I5 of the latter into the supply vessel I3 without attaining the discharge space proper. That portion of the glass tube I2 which leads to the interior of the discharge tube protrudes by an extension I6 into the supply vessel I3 and thus forms, jointly with the extension I5, a mercury trap which serves to prevent, in cooperation with the extension I5, the passage of liquid mercury to the discharge space during transport of the tube. The extensions I5 and I6 are covered by sheets of nickel gauze I'I and I8 respectively having a mesh width of 0.135 mm. and a wire diameter of 0.045 mm., which prevents spattering mercury when attaining the slit with a height of about 2 mms. between the extensions, from penetrating into the exhaust tube. The rectilinear shape of the latter tube is not altered by the above-described construction and the gauze does not constitute an appreciable obstacle to the passage of gases to be pumped away to the exhausting device or of the liquidV mercury, during the filling operation, in the direction ofthe supply vessel I3. In the last-mentioned case it is even advantageous that the ascending mercury is divided and slightly braked by the gauze. The construction described renders it superuous to burn out the tube anew when it is put into operation, for example after transport, for the purpose of removing excessive mercury which sticks to the electrode and is favourable to the production of back-ignition.

The tube, which is represented to scale inthe drawing, has a bulb diameter of 60 mms. and the annexed scale permits to determine the other dimensions of the tube in any easy manner. The incandescent cathode has a heating voltage of 5 volts'and a heating current of 14 amperes. rlhe .maximum mean value of the anode current which is allowable during operation amounts to 2,5 amps., the peak value being about l10 amps. According to regulations the tube can sustain in the blocking phase a maximum peak value of the voltage of 20,000 volts and for a short time this value may even arnountto 45,000 volts. There exists reason tor assume that this high load capacity is due not only to the particular construction of the complex of discharge vessel, cathode, cathode screen and anodelbut also to the fact Athat for the liquid mercury use is made of a supply vessel accordingto `the invention. It has been found thatin some cases tubes not'provided with a supply vessel Yaccording to the invention but for the rest constructed as shown in the figure could sustain in less high blocking voltages whilst with tubes according to the invention when submitted to tests of` long duration it could be ascertained that even after a comparatively long period of operation the discharge space proper had remained in a vremarkable manner free even from traces of liquid mercury.

With the form of construction represented to scalei in Fig. 2 constituent parts corresponding to those of the supply vessel according to Fig. `1 are denotedlby the same reference numerals whilst also in this case the dimensions may be determined by means .ofthe Aannexed scale. In this case the lengtheningpiece l5 has a funnelshaped extension 20 which terminates about at the height of the lower end of Athe lengthening piece I6, a cap, 2I of metal gauge being provided which takes up the lengthening piecel I6 in a pointed re-entrantpqrtion 22, the arrangement being such that liquid mercury coming from below is diverted by the point 22 of the tube l2-l6 and can easily attain the supply space through the funnel-shaped extension 2l! and the gauge 2l. The peculiarity of the construction is that it is impossible for the mercury in the vessel I3 when moving towards lthe discharge space to attain the tube |2IB whilst it does not cause any inconvenience if in the case of an opposite shock the mercury might come again through the cap 2| and the funnelshaped portion into the tube I5. In this case, with a renewed reversal of the movement, it is diverted again by the point 22 and falls back into the supply vessel. The dimensions of the construction must be so chosen that no excessive speed is imparted to the mercury, which may be achieved by maintaining the lengths of the free paths in the supply vessel as small as possible; preferably they should not be longer than double the diameter of the exhaust tube. This remark more particularly applies to the diameter and the length of the supply vessel `and as well to the construction of Fig. l as to that according to Fig. 2. These dimensions should, however, not be taken so small that due to capillarity the mercury may stick between the gauge and the neighbouring walls. Besides, it is advisable not to take an excessively large quantity of mer-l ber, one of said tubular portions forming a path` of low resistance to vapors between the space within the envelope and the space within the chamber, the seco-nd tubular portion serving to introduce a vapor-producing material into said chamber` and a supply of the vapor-producingv material within said chamber at one ofl said extending portions. Y

2. A discharge tube comprising an envelope, electrodes and a vapor lling within the envelope,

side of one an exhausting member connected to the envelope,

said member comprising a chamber portion and two tubular portions arranged in alignment and extending into said chamber, said tubular portions forming a space with said chamber portion and having their adjacent ends spaced apart to form an annular slit, a supplyv of vapor-producing material within said space, one of said tubular portions being connected to the space Y within the envelope, and the other tubular por y Y 3 alignment and extending into said chamber, said tubular portions forming a space with said chamber portion and having their adjacent ends spaced apa-rt to form an annular slit having a height of 3 mms. at the most, a supply of vaporproducingmaterial within said space, one of said tubular portions being connected to fthe space tion serving to introduce the vapor-producing material into the space formed in said chamber.`

4. A discharge tube comprising an envelope, electrodes and a vapor lling fwithin the enve- Y lope, an exhausting member connected to the envelope, said member comprising fa chamber 4 metallic gauze screen members disposed over said supply of vapor-producing material within the within the envelope, and the other tubular por.-

tion serving to introduceV the vapor-producing lmaterial into the space formed in said chamber.

3. A discharge tube comprising an envelope,

electrodes and a vapor filling within the envelope, an exhausting member connected tothe envelope, said member comprising a chamber portion and two tubular portions arranged in adjacent ends, a supply of vapor-producing material within the space formed in said chamber,

one of said tubular portions being connected to the space within the envelope, and the other Vtubular portion serving to introduce the vapor-` producing material into the space formed in said space formed in said chamber, one of the tubular portions being connected to the space Within the envelope, and the other tubular portion serving to introduce the vapor-producing material into the space formed in said chamber. l 6. A discharge tube comprising an envelop lelectrodes and a vapor filling within the envelope, an exhausting member connected to the envelope, said member comprising a chamber portion and two tubular portions arranged in alignment andextending into said chamber, one of the." tubularportions being connected to the space within the envelope, a substantially conical metallic gauze screen disposed over the extending end of said tubular portion, the second tubular ,Y

tubular portion serving to introduce a vaporproducing materialv into said chamber, and a supply ofthe vapor-producing material within portions.

MIN'NE KUIPERS. 

